Mystacidium venosum

Mystacidium venosum is from South Africa (Eastern Cape, KwaZulu-Natal, Mpumalanga, Limpopo), Eswatini (=Swaziland) and Mozambique (la Croix and la Croix 1998, Stewart et al. 2006).  The habitat could vary, including woodland, riverine bush, coastal and montane forests. In nature, this species flowers in winter time (April to July of Southern hemisphere in Stewart et al. 2006 and April to October in Wodrich 1997).  la Croix and la Croix (1997) mentioned that it bloomed in autumn and early winter (October and November) in their greenhouse.  The photos in this post were taken on March 9, 2017, but it was within 1 year after importation from Afri Orchids of South Africa, so it was still in Southern hemisphere time.  Subsequently, it started to flower in fall (late September).  It was making better displays, but I didn't take photos, and the plant unfortunately died in 2020.

M. venosum and M. capense have the longest spur (>4cm) in the genus.  These two species are similar, but the flowers of M. venosum are smaller.  M capense also flowers in spring time.

There is a study of the basic breeding system of M. venosum (Luyt and Johnson 2001), so here I mentions several interesting findings.

Habitat: They observed that the host plants include Ficus natalensis (Natal Fig), Ekebergia capensis (Cape Ash), Podocarpus latifolius (broad-leaved yellowwood), Mangifera indica (Mango), Cupressus spp. (Cypress), and Pinus spp (Pine).  It can be observed in both shady and very exposed positions.

Pollination biology: It is a hawkmoth pollinated plant.  They observed many pollination events, but could identify only two visitors; Nephele accentifera accentifera and Hippotion eson.  While the former is likely to be an effective pollinators because it was carrying 20 pollinaria of M. venosum, no pollinaria was attached to the later (it may have been stealing nectar).  M. venosum requires pollinators and no autonomous pollination (i.e. self-pollination without pollinators) was observed. However, with hand-pollination, it is capable of setting seeds with self-fertilization.  The fruits produced by self-fertilization was about half in weight of those produced by outcrossing, and selfed seeds contained embryos at much lower rate (37% vs 99%).  This suggests that they are partially self-incompatible or that there is a high level of early acting inbreeding depression (the embryo died during the seed development due to expression of genetic diseases). The nectar sugar concentration was 18% and included 87% sucrose, 10% fructose, and 3% glucose. The peak nectar production was around 8PM, and the plants appeared to reabsorb the nectar after 8PM.  Floral scent was produced from 5:30PM to 8PM, and it is mainly composed of Jasmine lactone (66%) and (􏰀E, E)- Farnesol (10%).  The flower lasts for a long time and the average life span of a flower was 24 days Pollination significantly reduce the longevity to 5 days.  Removal of pollinaria slightly reduce the longevity, too.  In the outdoor condition, viability of pollinia decreased with age, but some of them were viable to 10-20 days.  Flower age didn't seem to influence the fruit set rate, neither (they tested up to 10 day old flowers).

Wodrich (1997) recommend intermediate temeprature, 40-70% shade, and no dry winter rest. 

Literature Cited:

• la Croix, I. and E. la Croix. 1997. African Orchids in the Wild and in Cultivation.  Timber Press, Portland, Oregon (p. 258-259).
• Luyt, R., and S. D. Johnson. 2001. Hawkmoth pollination of the African epiphytic orchid Mystacidium venosum, with special reference to flower and pollen longevity.  Plant Systematics and Evolution 228(1-2): 49-62. (link to abstract, there is a link to full text from there)
• Stewart, J., J. Hermans, B. Campbell.  2006. Angraecoid Orchids - Species from the African Region. Timber Press, Portland, Oregon (p. 342)
• Wodrich, K. H. K. 1997. Growing South African Indigenous Orchids. CRC Press. (p. 126).